Etretinate administration reduces serum propeptide of type I procollagen level in patients with psoriasis

The serum carboxyterminal propeptide of type I procollagen (PICP) level in 26 patients with psoriasis was significantly lower than in control subjects (124 +/- 47 and 224 +/- 78 ng/ml, respectively; P < 0.001). The patients were divided into two groups, those treated with etretinate and untreated patients. PICP levels in the treated group were significantly lower than those in the untreated group (P < 0.001), but there was no difference between the control and untreated groups. In addition, there was a negative correlation between PICP levels and the serum etretinate concentration in treated patients (r = -0.622, P < 0.05). There was no difference between procollagen type III aminoterminal propeptide (PIIIP) levels in patients and controls, nor was there any significant difference between etretinate-treated and untreated patients. In cell culture studies, etretinate dose-dependently (from 10(-9) to 10(-5) M) decreased the PICP concentration in the medium of fibroblasts from both healthy subjects and patients. In osteoblast cell culture, PICP levels were reduced only in a high concentration of etretinate (10(-5) M). However, no change was observed in preadipose cells. Our in vivo and in vitro observations indicated that psoriasis per se did not affect either serum PICP or PIIIP levels, but that etretinate had an inhibitory effect on collagen synthesis by fibroblasts. Hence, the administration of etretinate to psoriatic patients is, at least in part, responsible for the reduction of serum PICP levels in these patients.